Term M1 Definition: The narrow-range monetary aggregate for the U.S. economy containing the combination of currency (and coins) issued by government and held by the nonbank public and checkable deposits issued by banking institutions. M1 contains the two items that function as THE medium of exchange for the U.S. economy. M1 is one of three monetary aggregates tracked and reported by the Federal Reserve System. The other two are designated M2 and M3.